Method for imparting durable press properties to cellulosic fabrics

ABSTRACT

NOVEL DIMETHYLOL - N,N&#39;&#39; - ALIPHATIC - BISIMIDAZOLIDONES HAVING FROM 2 TO 10 CARBON ATOMS IN THE ALIPHATIC GROUP ARE CAPABLE OF CROSS-LINKING WITH CELLULOSIC MATERIALS AND IMPARTING DURABLE PRESS PROPERTIES TO COTTON AND OTHER CELLULOSE-CONTAINING FABRICS WITHOUT MATERIALLY REDUCING THE TEAR STRENGTHS OF SUCH FABRICS.

United States Patent O 3,814,580 METHOD FOR IMPARTING DURABLE PRESS PROPERTIES TO CELLULOSIC FABRICS Gerfried Pruckmayr, Media, Pa., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del. No Drawing. Filed Feb. 16, 1971, Ser. No. 115,744 Int. Cl. D06m 15/54, 15/58, 99/02 US. Cl. 8-186 3 Claims ABSTRACT OF THE DISCLOSURE Novel dimethylol N,N' aliphatic bis-imidazolidones having from 2 to 10 carbon atoms in the aliphatic group are capable of cross-linking with cellulosic materials and imparting durable press properties to cotton and other cellulose-containing fabrics without materially reducing the tear strengths of such fabrics.

BACKGROUND OF THE INVENTION Although durable press cellulosic fabrics, such as cotton and cotton-polyester blend fabrics for example, treated with chemical agents to impart durable press characteristics have come into wide-spread use in recent years, they have suffered from the disadvantage that the available durable press treating agents have seriously reduced the tear strengths of the treated fabrics. This is true of even the most widely used commercial durable press treating agent, dimethyloldihydroxyethylene urea, which reduces the tear strength of treated cotton fabrics as much as 50% under usual treatment conditions.

The principal object of the present invention, therefore, is to supply the existing need for treating agents and methods to impart durable press characteristics to cellulosic fabrics without, however, seriously decreasing the tear strengths of such fabrics.

A lower homologue of the treating agents of the present invention, dimethylol N,-N'-methylene-bis-imidazolidone has been described in Hurwitz and Auten U.S. Pat. 2,613,- 210 as a treating agent for cellulose to impart crush resistance. Such crush resistance is important in the manufacture of fabrics having mechanical finishes such as glazing, schreinering, moireing and embossing, in which a pattern, applied to the fabric when it is in the wet plastic state, is set and rendered permanent on heating. Despite its utility in imparting crush resistance, the methylene homologue does not posses the unexpected ability of the higher homologues of the present invention to impart permanent press characteristics to cellulosic materials without seriously reducing the tear strengths of the treated fabrics.

SUMMARY OF THE INVENTION The present invention relates to novel treating agents and to a method for applying them to cellulose-containing fabrics to impart durable press properties to the fabrics without, however, seriously decreasing the tear strength of the fabrics.

The novel treating agents of the invention are compounds represented by the formula:

HOCHZN N-R-N N CH1 OH Patented June 4, 1974 ice groups containing 2 to 10 carbon atoms, both straight and branched chain, including saturated and ethenically or acetylenically unsaturated or poly-unsaturated groups, including, but not limited, to the following groups: ethylene, n-propylene, isopropylene, n-butylene, isobutylene, sec.-butylene, tert-butylene, and n-amylene, n-hexylene, n-octylene, n-nonylene, n-decylene and any branched chain isomer thereof, and any of the foregoing groups containing one or more double or triple bonds within the straight or branched chain.

The novel method of the invention comprises application of these compounds to cellulosic fabrics by padding them onto the fabric from an aqueous solution, air drying the impregnated textiles, and finally heat-setting them to induce crosslinking.

DETAILED DESCRIPTION OF THE INVENTION HzNCHzCHzNHCHzCHzCHaNHCHz CHzNHz HzN C O NH;

nocmr r N-CHzCHzCHz- NCHQOH The synthesis of the preferred ethylene compound, dimethylol N,N' ethylene bis imidazolidone is carried out in the same way by condensation of triethylenetetramine with urea and reaction of the resulting product with formaldehyde. The other compounds of the invention, in which the aliphatic group contains from 4 to 10 carbon atoms, are also prepared by the same general procedure.

It should be noted, however, that while the nature of the initial reactants is the same in all cases with the alkylene dihalides, the initial reaction product varies. More specifically, ethylene dibromide and n-propylene dibromide give linear tetramines in high yields when reacted with ethylene diamine. n-Butylene dibromide and dichloride, on the other hand, form N-aminoethylene-pyrrolidine exclusively. n-Pentamethylene dibromide forms the corresponding piperidine. n-Hexamethylene dibromide again gives the expected linear tetramine. All other acyclic diethylene tetramines, including those obtained from the branched chain 3 to 10 car-bon atom alkylene dihalides, or other aliphatic dihalides, which cannot form 5- or 6-membered rings with ethylene diamine, produce the corresponding dimethylol N,N' aliphatic-bis-imidazolidones when condensed with urea and reacted with formaldehyde according to the general procedure set forth above.

The invention will be more readily understood from a consideration of the following specific examples which are given for the purposes of illustration only and are not intended to limit the scope of the invention in any way.

EXAMPLE 1 Preparation of diethylene-n-propylenetetramine To a solution of 85 g. of ethylene diamine in 25 g. of water were added, dropwise, 50 g. of 1,3-dibrornopropane in 80 ml. of ethanol. The resulting mixture was refluxed for two hours. After cooling, 70 g. of solid potassium hydroxide were added and the mixture was stirred overnight and again refluxed for two hours. The solids were removed by filtration. Then the excess ethylene. diamine was removed from the filtrate by distillation under atmospheric pressure until the head temperature reached 120 C. The residual oil was treated with more solid potassium hydroxide and refiltered. The resulting product, obtained by distillation under water vacuum, had a 'boiling point of ISO-170 C. Yield: 25 g. (63%). The product was identified as diethylene n-propylenetetramine by its NMR spectrum: signals at 101 c.p.s., 143 c.p.s., and 163 c.p.s. in the ratios of 1:3:6.

EXAMPLE 2 Preparation of diethylene-n-hexamethylenetetramine Ethylene diamine (85 g.) in 25 g. of water was reacted with 62 g. of 1,6-dibromohexane in 100 ml. of ethanol according to the procedure of Example 1 above. Yield: 24 g. (48%), B.P. 140 C./1 mm.

Preparation of diethylene decamethylenetetramine Ethylene diamine (85 g.) in 25 g. of water was reacted with 75 g. of 1,10-dibromodecane in 100 ml. of ethanol/dioxane (1:1) according to the procedure of Example 1 above. A yellow oil was obtained which did not distill below 230 C. at 1 mm. Yield: 36 g. The dimethylol derivative had a melting point of 117 C.

Triethylenetetramine is a commercially available material. The 4-, 5-, 7-, 8- and 9-carbon atom alkylene tetramines, both straight and branched chain, and the branched chain 3-, 6- and IO-carbon atom alkylene tetramines also can be obtained according to the general procedure of Example 1 above substituting the appropriate alkylene dihalide for the dibromopropane of that Example. The identity of the various tetramines prepared in this way was confirmed by gas chromatographic analysis employing a column containing 10% silicone grease on Chromosorb adsorbent material, helium as the carrier gas at a flow rate of 40 cc./min. at temperatures of 50 to 210 C. chart speed of 1 in./min., injection temperature of 200 C. and detection temperature of 290 C. with a temperature program of 20 C./min. The reaction products of ethylene diamine with ethylene dibromide and propylene dibromide gave the expected linear tetramines. As noted above, n-butylene dibromide and dichloride, when reacted with ethylene diamine, produced N-aminoethylene pyrrolidine. The n pentamethylene dibromideethylene diamine reaction product was the corresponding piperidine and n-hexamethylene dibromide gave the expected linear tetramine.

4 EXAMPLE 4 Preparation of dimethylol-N,N-ethylene-bisimidazolidone Calculated Analysis, percent CsH14N4Oa Found Carbon 48. 47 48. 45 Hydrogen 7. 17 7. 09 Nitrogen 28. 27 28. 70

B. The product of part A was then reacted with formaldehyde to produce dimethylol N,N' ethylene-bis-imidazolidone. The reaction was carried out in the following manner: 10.5 g. of ethylene-bis-imidazolidone were dissolved in an excess of commercial formaldehyde (37% aqueous solution) at room temperature. The solution was brought to the boiling point, and then allowed to cool to room temperature. The excess of water and formaldehyde was then removed by distillation under reduced pressure in a rotating evaporator. The residual thick syrup was diluted with methanol. On standing, a thick mass of white crystals separates. The crystals are collected by filtration, washed with methanol, and dried. Yield: 10.4 g. Melting point: 171 C.

The procedure of Example 4 was repeated substituting diethylene propylenetetramine, prepared according to Example 1, for the triethylenetetramine in appropriate amount. The resulting N,N'-n-propylene bis imidazolidone, obtained in yield, had a melting point of 185-187 C. The structure of this compound was verified by NMR which showed a broad amide peak centered at 380 c.p.s., a sharp ethylene singlet at 199 c.p.s., a triplet centered at 174 c.p.s. (from the two N-methylene groups of the propylene bridge), and a quintet at c.p.s. (from the center methylene group), all in the correct ratios of 1:422: 1, respectively.

This material was then reacted with formaldehyde according to the procedure of part B of Example 4 to obtain the desired product, dimethylol-N,N'-n-propylene bis-imidazolidone which had a melting point of 117 C. A purified sample melted at C. and had the followmg composition.

EXAMPLE 6 Preparation of dimethylol-N,N'-hexamethylene-bisimidazolidone 'Diethylene hexamethylenetetramine (10 g.) prepared according to Example 2, plus 6 g. of urea were heated slowly to 210 C. during a period of four hours. The melt which crystallyzed on cooling, was recrystallyzed from methanol to yield N,N-hexamethylene bis-imidazolidone, which had a melting point of 14'8-149 C.

This product was then reacted with formaldehyde according to the precedure of part B of Example 4 to obtain the desired product, dimethylol-N,N'-hexamethylenebis-imidazolidone, which had a melting point of 115 C.

EXAMPLE 7 Preparation of dimethylol-N,N'-decamethylene-bisimidazolidone Calculfiated or- Analysls, percent ClOHJUNiOi Found Carbon 61. 90 61. 30 Hydrogem- 9. 74 10. 47 Nitrogen 18. 05 17. 73

B. The product of part A above was reacted with formaldehyde according to the general procedure described above to obtain the desired dimethylol-N,-N'-decamethylene-bis-imidazolidone which was a colorless oil.

All other dimethylol-N,N'-aliphatic-bis-imidazolidones of the invention containing 2 to 10 carbon atoms in the aliphatic group can be prepared by the general procedure described above.

The new treating agents are generally applied to the fabrics to be treated by a padding operation. The fabric is impregnated, for example by submerging it in an aqueous solution containing about 515% of the treating agent by weight. The excess solution is removed by passing the impregnated fabric between rubber-coated rolls of a laboratory wringer, and the wet fabric is dried in air or in a force-draft oven at temperatures below 100 C. The fabric is now ready for the final durable press curing cycle, as described later.

The wet pick-up of the fabric will, of course, depend upon the thickness of the fabric, i.e. thin fabrics will pick up a larger percentage of their weight of treating solution than thicker and heavier fabrics. In general, however, the wet pick-up of treating solution will be about 80 to 100% of the weight of the fabric treated.

The dried treated fabrics are then cured at temperatures in the range from about 120 to 170 C. for periods of about 3 to 5 minutes. In general, it is desirable to minimize both the time and temperature of the curing cycle consistent with obtaining an adequate cure. The preferred curing cycle is about 3 to 5 minutes at a temperature of no more than 150 C. A cycle of about 5 minutes at 160 C. represents about the maximum permissible curing conditions, since under more severe conditions most fabrics will begin to degrade and yellow. Shorter curing times, for example, three minutes, may be permissible at curing temperatures up to 170 C., although some yellowing may result. While temperatures as low as 120 C. may be used, the cure obtained may not be complete.

treated cotton is rather low, about 150, increasing to 189 The dry add-on of treating agent after curing will be in the range of about 5 to 20% of the weight of the fabric, the preferred dry add-on being about 10 to 15% for dura ble press characteristics; less than 10% down to about 5% will impart wash and wear properties only. More than about 15 add-on tends to stiffen the fabric and is unnecessary.

A series of tests were carried out under varying conditions to evaluate the compounds of the invention as durable press agents and appropriate control samples. The substrate in all cases was pure cotton broadcloth, type 5A, Style 403 available from Spring Mills, NY. The wrinkle recovery, tear resistance, and fabric stiffness of this material were tested, first as received [Table I (A)], and then after removing the sizing by boiling the sample for 15 minutes in a 0.25% aqueous solution of the sodium salt of an unsaturated long chain alcohol sulfate, (available from E. I. du Pont de Nemours and Co. as Duponol 'D), followed by thorough rinsing and drying [Table I(B)]. The degradation of the sample fabric by heat alone was also studied. Samples C to G (Table I) are the test results of the desized broadcloth after a five minute exposure to different temperatures.

The tear strengths in the warp (W) and filling ('F) directions were determined by the Elmendorf method method (ASTM D-1424). In this test, an exactly measured length of fabric (43 mm.) is torn by a falling pendulum and the tearing force in grams is determined. The tear strength of the warp is always higher than that of the filling. Furthermore, a drastic decrease in tear strength on exposure to heat is evident. After five minutes at 170 C. the tear strength decreased to approximately 50% of the original values in both the warp and filling directions. A typical curing cycle for commercial durable press setting materials is about five minutes at ISO- C.

The next column in Table I sets forth the fabric stiffness as determined by the Cantilever Test (ASTM D- 1388). In this test, the length of overhang of a 25 mm.- wide sample of fabric is measured when the tip of the test specimen is depressed under its own weight to the point where the line joining the tip to the edge of a horizontal platform forms an angle of 41.5 degrees. The cube of half the overhang length (%=bending length) multiplied by the unit weight (W of the fabric (desized broadcloth: 12.0 mg./cm. is defined as flexural rigidity In Table I only the flexural rigidity in the warp direction is reported, since the change in the filling direction was not as pronounced (from G =40.5 to G =58.7 after five minutes at C.).

The last column in Table I sets forth the recovery angle, determined by the vertical strip apparatus (ASTM D1295). A test specimen is creased under controlled conditions and the recovery angles in both directions (W+F) are measured and added. A 100% recovery would, therefore, correspond to an angle of 360 (W+F). As can be seen in Tabel I, the recovery angle of unafter heat treatment, which may produce some crosslinking and increased flexural rigidity.

These values were measured at room temperatures and 75 to 85% relative humidity. A comparison between a completely dry sample (vacuum desiccator) and a wet sample is shown in Table II. The tear strengths are not very different, although the wet warp tear strength is noticeably higher (1650 g.). The recovery angles are also in the same range; the wet recovery angles being slightly lower.

TABLE I.TEAR STRENGTH RIGIDIIY, AND RECOVERY ANGLE OF COTTON BRoADCLOTH (A, STYLE 403) UNDER DIFFERENT CONDITIONS Tear strength (g.) Flexural Recovery rigidit angle 5 Condition W F (owl (W+F) (A) As received 1,150 800 69.6 166 (B) Secured 15 min in 025 7 DuponolD 1,220 1,140 55.7 133 (C) Aiter5minutes at 120 840 700 58.7 152 (D) After5minutes at 130 0-. 1, 000 960 144.0 145 10 (E) Aiter5minutes at 140 0.- 720 520 104.5 106 (F) After 5 minutes at 150 0. 710 540 104.5 162 (G) After 5 minutes at 170 0-. 660 500 105.5 189 TABLE II.-CONTROL SAMPLES TESTED AT DIFFERENT LEVELS OF HUMIDITY Tear strength (g.) Flexural Recovery rigidity angle Test conditions W F (Gw) (W+F) (A) Room temperature 75% relative humidity fabric 1,220 1,140 58.7 140 11.75 111g./cm. -1- 1,200 000 162.4 149 (0) Wet fabric wt., 19.8 mg./

The recovery angles (W+F), tear strength (T and fiexural rigidity (G of crosslinked cotton (5A, Style 403 cotton broadcloth) treated for 5 minutes at temperatures of 130 C., 150- C. and 170 C. with several permanent press agents of the prior art, and certain compounds of the present invention are compared with control samples in the following table. These tests were conducted according to ASTM D-1295, ASTM D-1424, and ASTM D-1338, respectively.

In the preceding series of tests in which all of the crosslinking agents are employed at the same concentration (10%) by weight of the fabric sample, the number of crosslinking sites decreases as the molecular weight of the treating agent increases from dimethylol-N,N'- ethylene-bis-imidazolidone through the higher alkylene homologues up to the decamethylene compound (not shown in the table). While the recovery angles of the samples decreased with increasing molecular weight, the tear strengths increased substantially to about 150% of the tear strength of the control for the hexamethylene compound.

In still another series of tests (Table V) with samples of the same fabric the number of methylol groups was kept constant (0.068 mole percent), based on the weight of the fabric, for each of the different treating agents tested. When the number of crosslinking sites was kept constant in this way, the recovery angles of the different samples remained constant also, within experimental error, apparently regardless of chain length in the alkylene group. The tear strengths of the different samples were not found to be as constant as the recovery angles, the highest value being that observed for dimethylol-N, N'-ethylene-bis-imidazolidone (735 g.). Flexural rigidity did not change materially in either of the two preceding series of tests as seen in Table V below. In both of these series of tests the tear strengths of the samples treated with the compounds of the invention remained well above those of samples treated with the durable press agents of the prior art.

TABLE III.-RECOVERY ANGLES (W+F), TEAR STRENGTH (TW), AND FLEXURAL RIGIDITY OF CROSSLINKED COTTON Setting Warp temp., Recovery tear Flexural C. angle strength rigidity crosslinking agent (65% wet pickup) minutes) (W+F) (Tw) w) Contr 130 154 1, 060 144 150 162 710 164 170 189 660 165 Formaldehy 130 228 150 253 170 213 D imethylol ethylene urea (prior art) 130 248 150 248 170 260 Dimethyiol dihydroxyethylene urea (commercial durable press agent) 130 302 150 306 170 312 Dimethylol-N,N'-ethylene bis-imidazolidone 170 302 Dimethylol-N,N'-propylene bis-imidazolidone 130 258 In another series of tests samples of the same fabric were treated for 5 minutes at 150 C. with identical concentrations (10% by weight) of the dimethylol crosslinking agents and compared to a control. The results of these tests are set forth in Table IV below.

TABLE IV.RECOVERY ANGLES (W+F), TEAR STRENGTH EI6VQT1E3ID FLEXURAL RIGIDITY (GW) OF CROSSLINKED [Concentration 10% by weight cure: 5 minutes at 150 0.]

TABLE V.REOOVERY ANGLES (W+F), 'IEAR STRENGTH ((SIOVXQTCASD FLEXURAL RIGIDITY (GW) OF CROSSLINKED [Concentrationz 0.068 mole percent; Cure: 5 minutes at 0.]

Warp Recovery tear Flexural angle strength ri 'dity crosslinking agent (W+F) (TW) GW) Control 162 710 164 Dimethylol ethylene urea. 309 445 133 Dimethylol-N,N-ethylene imidazoiidone 297 710 151 Dimethylol-N,N-propyl imidazolidone 311 615 103 Dimethylol-N,N-hex bis-imidazolidone 300 680 167 Dimethylol-N,N'-deea1nethylene bis-imidazolidone 275 635 As noted previously the primary object of the present invention is to provide new durable press agents which do not degrade the treated fabric and substantially reduce its tear strength as is the case with previously available durable press agents. The currently most widely used commercial durable press agent, dimethylol dihydroxyethylene urea, as shown in Table HI above decreases the tear strength of cotton fabric more than 50% after a minute cure at 130 C. Dimethylol ethylene urea, another widely used textile finishing agent, decreases the tear strength of the fabric by over 40% under the same conditions. The compounds of the present invention dimethylol-N, N'-ethyleneand propylene-bis-imidazolidone, also as shown in Table III, decrease the tear strength of the fabric less than 25% for the propylene compound and only about 2% for the preferred ethylene compound, while maintaining recovery angles nearly as high as those of the most used commercial durable press agent, dimethylol dihydroxyethylene urea. As seen in Table IV, where fabric samples were treated 5 min. at 150 C. with by weight of the durable press agents, the prior art agents again seriously decreased the tear strength of the fabric whereas the ethylene and propylene homologues of the compounds of the invention did not decrease the tear strength at all and the hexamethylene compound actually increased the tear strength by 50%. Under the equal mole percent conditions of Table V, the commercial compounds again seriously decreased tear strength while the ethylene homologue of the new compounds did not reduce tear strength at all and relatively small reductions in tear strength were obtained with the propylene and hexamethylene homologues.

The dimethylol-N,N'-alkylene-bis-imidazolidone comcompounds of the present invention in which the alkyleue group contains from 2 to 10 carbon atoms surprisingly impart durable press properties to cellulose-containing fabrics without seriously reducing their tensile strength.

What is claimed is:

1. A method for imparting durable press properties to a cellulosic fabric which comprises impregnating the fabric with an aqueous solution containing about 5 to by weight of a treating agent, removing excess treating solution and drying the fabric in air at a temper- 10 ature below about C., and curing the treating agent at a temperature in the range from about to C. for a period of 3 to 5 minutes, to obtain a treated fabric having a dry add-on of cured treating agent of about 5 to 20% by weight of the fabric, wherein said treating agent is a compound of the formula:

in which R is a straight chain alkylene group containing 6 to 10 carbon atoms.

2. The method of claim 1 in which the treating agent is dimethylol-N,N'-hexamethylene-bis-imidazolidone.

3. The method of claim 1 in which the treating agent is dimethylol-N,N'-decamethylene-bis-imidazolidone..

References Cited UNITED STATES PATENTS 2,874,149 2/ 1959 Applegath et a1. 260309.7 2,613,212 10/ 1952 El-Iurwitz et al. 260309.7 2,777,857 1/ 1957 Konig 260-3097 2,876,062 3/1959 Torke 260-309] 2,924,605 2/ 1960 Hughes 260-309] 2,926,169 2/ 1960 Hughes 260309.7 3,313,788 4/1967 Convert et a1 260-309] 2,613,210 10/ 1952 EHurwitz et al 260309.7 3,567,361 3/1971 Vail 8-1163 GEORGE F. LESMES, Primary Examiner J. CANNON, Assistant Examiner US. Cl. X.R. 

